The smallest component in small arms ammunition, the primer, is the link between the striking of the firing pin and the explosion of the projectile out of the cartridge casing. Generally, most common primer mixes are comprised of a primary explosive, an oxiding agent and a fuel source. Percussion primers and/or primer mixes have undergone relatively few gradual changes since their original development. In early primers, mercury fulminate was the most commonly used primer mix. Since that time, alternate priming mixes have replaced mercury fulminate, as this latter composition was found to deteriorate rapidly under tropical conditions and cause potential health problems or concerns such as lethargy and nausea to the shooter after firing. Such alternate mixes, typically based on lead thiocyanate/potassium chlorate formulations, however, were found to be detrimental to weapon barrels because of the formation of corrosive water soluble potassium chloride salts upon combustion. More conventional primer mixes currently in use typically are based on the primary explosive lead styphnate, a substance which is much more stable than mercury fulminate and is in common use today.
Although more stable and less corrosive than earlier primer mixes, the use of lead styphnate-based primers has become more of a concern recently due to increasing awareness of the health hazards of lead. While considerable attention has been directed to removing lead from primer mixes, however, there has been less attention paid to the removal of the remaining toxic components from the primer mix. One of most common oxidizing agents used in conventional primer mixes is barium nitrate. Unfortunately, barium is highly toxic, and therefore poses a potential health hazard, particularly when used within an enclosed shooting area where it can accumulate in the atmosphere and on surfaces. Generally, a typical small arms primer contains between 30% and 50% oxidizer, so replacing barium nitrate with a non-toxic oxidizer greatly reduces the post-ignition airborne hazards.
Alternative oxidizers, such as potassium nitrate, have been found to perform as well as barium nitrate under certain circumstances or conditions. For example, inorganic nitrate salts perform very well as oxidizing agents in pyrotechnic formulations because of their relatively low melting points, available oxygen, and their crystalline form; however, such nitrate salts such as potassium nitrate, are hygroscopic, making them very susceptible to the effects of atmospheric moisture and inappropriate for use in certain storage conditions. Since priming formulations typically are assembled in high moisture environments to escape unintended ignition by heat, shock, or impact, many oxidizers, such as inorganic nitrates, can cause deleterious side chemical reactions when combined with other ingredients under such high-moisture conditions. Such reactions produce an inferior product with reduced sensitivity to impact and thus ignition, consequently increasing potential failure rates for such primers.
Accordingly, there exists a need for a priming mixture for small arms ammunition that addresses the foregoing and other related and unrelated problems in the art.